This invention relates generally to alkyd polymer coatings and more specifically to modified alkyd resins useful in coatings and methods for making such resins.
Coatings for wood surfaces desirably have rapid dry times, good tannin blocking, good resistance to picking up dirt, good hot box stability and good exterior durability. While coatings having these properties to some extent are known, improvements in such properties, especially tannin blocking, are still needed.
Tannin is a group of soluble compounds that occur naturally in wood and plant material. The solubility of tannin allows tannin compounds to leach through the wood and the coating thereby forming stains on the surface of the wood or coating. Removal of the tannin from the wood substrate is not practical so the tannin leachate must be blocked from reaching the surface in order to avoid staining. Control of tannin leaching by adding chemical compounds with active ions to the coating prior to application is well known in the art. However, such additives typically have adverse impacts on other properties of the coating, such as viscosity, stability or longevity and/or are not environmentally friendly.